Although major depressive disorder (MDD) is heterogeneous and has low heritability, a genome-wide association study in humans has implicated Type III adenylyl cyclase (AC3) in MDD. Our previous reports and preliminary data demonstrate that AC3 global knockouts exhibit depression-like behaviors and other related phenotypes including altered sleeping pattern, an eating disorder and reduced basal synaptic transmission in hippocampal CA1 neurons. These support AC3 as a candidate gene associated with depression. However, since AC3 is widely expressed in cilia of many tissues, the roles of AC3 in the brain are not clear and we don't know in which area(s) of the brain the AC3 deficiency causes depression-like phenotypes. To dissect the function of AC3 in the brain and elucidate its involvement in depression, an AC3 floxed mouse strain was generated. The AC3 floxed mouse strain is being crossed with the EMX1-Cre mouse strain to specifically ablate AC3 in the forebrain. I will use molecular biological, behavioral, electrophysiological and in vivo imaging tools to investigate the roles of AC3 in the forebrain. Given that AC3 in olfactory cilia controls activation of olfactory sensory neurons, I will test if AC3 in primary cilia similarly regulates neuronal electrical activity in central neurons. This project will also examine if disruption of AC3 in the forebrain lead to depression-like behaviors in mice. In addition, I will deliver AAV1-expressing Cre recombinase to the hippocampus and nasal cavity of AC3 floxed mice respectively to ablate AC3 specifically in the hippocampus and olfactory epithelia. These tissue-specific knockouts will allow me to probe the function of AC3 in different locations and test its association with depression. I will further examine if ketamine and fluoxetine can rescue the depressive phenotypes respectively if conditional AC3 knockouts exhibit depression-like behaviors. This study could elucidate AC3 function in primary cilia in central neurons and validate if AC3 is a depression gene. It may point to a new avenue for developing antidepressants that specifically target G-protein coupled receptors in primary cilia in the brain.